Sound signaling apparatus



NOV. 19,1946. L Q CLEMENT 2,411,146

SOUND SIGNALING APPARATUS Original Filed June 14, 1933 INVHQTOR. Ivan C.CLEMENT Patented Nov. 19, 1946 UNETED srnrss SOUND SIGNALING APPARATUSIvan C. Clement, Greenwood, Mass., assignor, by

mesne assignments, to Submarine Signal Company, Boston, Mass, acorporation'of Delaware Original application June 14, 1933,- Serial No.

675,700. Divided and this application September 29, 1936, Serial No.103,163

The present invention is a division of my cpending application SerialNo. 675,700, filed June 14, 1933. a v

The present invention relates to an apparatus for transmitting andreceiving submarine or subaqueous signals, and more in particular to theuse of compressional waves in a frequency range above or near the upperlimit of audibility of the human ear.

The invention further relates to the transmission of a directive beam ofcompressional waves with the use of piezo-electric crystals which may bequartz. but preferably areRochelle-salt crystals or crystals havingsimilar piezo-electric properties.

In the present invention crystals of the Rochelle-salt type are not usedpurely as a socalled compressional crystal in which a compreselectrode.

The device of the present application may in particular be used toreceive supersonic waves within a broad range-of frequencies and by the8 Claims. (01.177-386) central piece 2 at thebottom of the casing. Thissupport may be circular so that the whole device canbe mounted in abearing and rotated about a vertical axis. The casing I, which may be ofmetal, is provided with a heavy back plate 3 which tapers somewhat tothe top of the apparatus as shown more particularly in Fig. 2.

I Within the back plate 3 is a recess within which a plurality ofpiezo-electric crystals is mounted. Each of the crystals 25 is supportedby rubber corners 26, 21 and 28 into which the corners of the crystalfit. Each crystal is provided with electrodes 29 and 30 on oppositesides thereof. The electrode 29, as indicated, may be connected toconductor 3i and the electrode 30' to the conductor 32. All the crystalsmay in this manner be the free corners of the crystals and through useof a plurality of crystals substantially aligned in the same planecovering a large surface as compared with the wave length of the wavewhich is being transmitted or received. A directional beam may betransmitted when the device is used as a transmitter orthe device mayact as a directional receiver, in which case it receives waves fromsubstantially one direction.

The apparatus will be more fully described in connection with theydescription of the embodiment illustrated in the drawings in which Fig.1

shows a plan view of the apparatus with the diaphragm and cover plateremoved; Fig. 2 shows a sectional view along the line 2-2 of Fig. 1;Fig. 3 shows an enlarged perspective view of the arrangement of anindividual crystal; and Fig. 4 shows a perspective view of amodification of Fig. 3.

With reference to Figs. 1, 2 and 3 of the drawings a plurality ofcrystals 25 is mounted w thin a casing -lwhich is supported preferablyby a connected in parallel with each other or in some other desiredmanner. The corners 28, 21 and 28 supporting the three comers of thecrystal may be of any yielding material such as molded rubber but Iprefer to use the substance which is known as glyptal and is a syntheticrubber possessing the desirable quality that it. is yielding but hasonly slight elasticity. .1

are held in position in the casing i by means of the plate 33 which issupported on a shoulder 34 in th cttsing by means of the screws 35. Theplate 33 is perforated at points corresponding to these perforations therods 36, 31, 38, etc., operate transmitting acoustic vibrations to the'free corners of the crystals. The rods themselves may be of rubber orother molded material or they may be metallic. The rods are by one endfirmly attached to the crystals and by the other end to a diaphragm 39which is preferably made of soft rubber. The diaphragm 39 can be held inplace by a clamping ring 20 suitably fastened to the 40 back of thecasing by means of th screws 2| arranged around the periphery of thecasing.

In the operation of the devic the sound wave .energy impressed vupon thediaphragm 39 is transmitted through the rods 36, etc., to free portionsof the crystals, thereby causing a bending of the crystals between thefree and supported corners. This bending creates a potential differencebetween the faces of the crystals which is detected in the receiver orreceiving circuit.

If the device is used as a transmitter, electrical energy is applied tothe electrodes of the crystals and the latter are made to bend in thesame manner as they are bent when excited by compressional waves. Itwill be noted that the crystals 59) are placed in substantially the sameplane and w time:

The crystals with the molded comers attached that the rods connectingthe diaphragm with th crystals end in substantially a single plane. Withthis arrangement the sound energy approaching normal to the surface ofthe diaphragm excites all of the crystals in the same phase while thesound energy approaching from any but a normal direction excites thecrystals out of phase.

In this way it will be readily understood that the device is highlydirectional in a direction normal to the surface of the diaphragm.

In Fig. 4 a slightly difierent form of crystal structure is shown. Inthis figure two similar crystals 40 and M are mounted in face to facecontact with an electrode between them. The crystals are arranged sothat the same polarity is produced at the top and bottom electrodes ofthe combination with the other polarity on the common electrode betweenthe two crystals. The crystal structure or unit illustrated in thisfigure may be substituted for that shown in Fig. 3 and will operate andact in substantially the-same way but with an enhanced effect.

Having now described my invention, I claim:

1. A submarine transceiver including a casing having a rigid backelement, a plurality of piezoelectric crystals of the Rochelle salt typehaving two parallel flat surfaces of polygonal shape, means formountingsaid crystals in said casing in substantially the same plane,supporting the same at some of the corners thereof and meansacoustically connecting said crystals to the propa' gating medium toexert acoustic vibrations on at least one of the unsupported cornersthereof.

2. A submarine transceiver including a'casing having a rigid backelement, a plurality of-piezoelectric crystals of the Rochelle salt typehaving two parallel fiat surfaces of polygonal shape, means for mountingsaid crystals in said casing in substantially the same plane, said meansincluding corner elements for holding said crystals and means holdingsaid corner elements in place, and means acoustically connecting saidcrystals to the propagating medium to exert acoustic vi-, brations onthe unsupported corners thereof.

3. A submarine transceiver including a casing having a rigid backelement, a plurality of piezoelectric crystals having two parallel fiatsurfaces of polygonal shape, means for mounting said 4. A submarinetransceiver including a casing having a rigid back element, a pluralityof piezoelectric crystals having two parallel flat surfaces ofquadrilateral shape, means for holding said crystals by three corners insubstantially the same plane, a diaphragm and a plurality of rods eachsecured to the free corners of each of said crystals and to saiddiaphragm.

5. A- submarine transceiver including a casing having a rigid backelement and a recess in one face thereof, a plurality of piezo-electriccrystals of prismatic shape, means for mounting said crystals in saidrecess leaving at least one comer of each crystal free, a diaphragmsecured to said casing and adapted to cover said recess and means forconnecting the free corners of the crystals to said diaphragm.

6. A submarine transceiver including a casing having a rigid backelement and a recess in one face thereof. a plurality of piezo-electriccrystals of prismatic shape, means for mounting said crystals in saidrecess leaving at least one corner of each crystal free, a plurality ofrods, one secured to a free portion of each crystal, a plate having aplurality of apertures therein adapted to fit over said rods innon-contiguous relation thereto and adapted to be secured to said casingand a diaphragm secured to each of said rods and to said casing foracoustically connecting the rods to the sound propagating medium.

7. An electromechanical,interchanging device, comprising in combination,a diaphragm, a casing, a plurality of piezo-electric crystal units,means for mounting said crystal units within said casing substantiallyin the same plane for flexural movement with at least a portion of eachunit free from the mounting means and individual means for connectingsaid units at least at the unsupported portions thereof to the diaphragmat a plurality of spaced points over the same.

8. An electromechanical energy interchanging device comprising, incombination, a diaphragm, a casing, a plurality of piezoelectric crystalunits, means mounting and supporting said crysta units in some areasnear the side edges thereof within said casing with the crystal unitspositioned substantially in the same plane, and individual meansconnecting each of said crystal units in areas at other side edgesthereof to the diaphragm at a plurality of spaced points over the same,said crystal units being otherwise unsupported in said last-mentionedareas whereby said crystal units are operated with a flexural movement.

- IVAN C. CLEMENT.

